Global warming disrupts animal development, study finds

fish eggs
This image shows different stages of development of fish eggs to the level of larval stage. Credit: Julian Uribe-Palomino

Future global warming could have major implications for animal population numbers with higher temperatures already affecting embryo development, scientists have warned.

Professor Dustin Marshall, from the Monash University School of Biological Sciences, and Director of the Centre for Geometric Biology, led an international research team which examined temperature, metabolic and developmental rates during development.

The findings are published today in the prestigious journal Nature Ecology & Evolution.

“Animals have to develop from an egg to a functioning organism and, with the exception of mammals, this takes place in the outside world and is very sensitive to changes in temperature,” said Professor Marshall.

“We found that animals have finely tuned physiologies so there is a near perfect relationship between the temperature that minimises the costs of development and the temperature in which species currently live,” he said.

“Our work reveals previously unrecognised sensitivities to global temperature increases.”

The study describes how as developmental costs increase past a species’ optimum, mothers must invest more resources in each offspring in order to offset these increase costs – when offspring become more costly to make, mothers must make fewer babies

The study found that there is a narrow band of temperatures that can minimise developmental costs for a wide range of species.

Temperatures that are too high or too low for that organism cause massive blow-outs in the ‘energy budget’ of the developing embryo.

The research team mined the published literature for data on temperature, metabolic and developmental rates during development.

They combined this data in a mathematical model that allowed them to predict the temperature that best minimised energy use during development for 71 very different taxa, from tropical crocodiles to Antarctic krill.

“Predictions of how future temperature changes will affect organisms are often based on estimates of how temperature affects survival,” said Professor Marshall.

“Our study shows that developmental costs are about twice as sensitive to temperature changes compared to survival measures, which means that we may have been underestimating the impacts of quite subtle temperature changes on development.”

For tropical marine species in particular, Developmental Cost Theory predicts that most species are already experiencing temperatures that exceed the optimum for minimising developmental costs.

“These species must either evolve new temperature dependencies of development or face rising costs and suffer reduced population replenishment now and in the future,” Professor Marshall said.

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